1002 Transactions of the American Institute. 



tendency of the intense current, to pass through from layer to 

 layer of the wire, and injure the coil. This division, however, 

 i)f an intensity coil was not new at this time, the same device 

 having been patented in England by Edward and Charles Bright, 

 October 21, 1852; No. of patent, 14,331. (See 14th claim.) It was 

 applied to the coils of relay magnets, but for the same purpose and 

 upon the same principle as PoggendorlTs suggestion. In 1856 the 

 coil began to make some stir and progress among electricians, and 

 gave a new-impulse to the use of the induction coil. In 1853 

 Fizeau, while investigating the subject of induction, found great 

 annoyance from the irregular action of the primary current. When 

 the sparks of the circuit-breaker were brilliant, the intensity of 

 the secondary was diminished, and when some obstruction occurred 

 to diminish the sparks, the secondary was increased. The irregular 

 action arose from the burning away of the points of contact by 

 the primary or extra current. He sought, therefore, to diminish or 

 absorb this current, by interposing a Leyden jar or a condenser. 

 By connecting the plates of the condenser with each side of the 

 interrupter or circuit-breaker, he found at once that the sparks 

 were diminished, while those of the secondary circuit were doubled 

 in length. {Comjptes Rendus, vol. 36, p. 420, 1853.) He also 

 suggested the convenience of placing the condenser beneath the 

 machine, and alluded to the effect of a long fine wire in suppressing 

 the extra current. Ruhmkorff soon applied Fizeau's condenser to 

 his coils, and exalted the intensity of the secondary so as to increase 

 the spark from one-eighth, or thereabouts, to a little over half 

 an inch in length. 



The only decided novelty of any particular value in the con- 

 struction of the coil was made in this country by Mr. Edward S. 

 Ritchie, of Boston, -Mass., in 1852. In a letter from Mr. Ritchie to 

 SilUrnan^s Journal, dated Boston, May 2, 1857, he describes a coil 

 with a peculiar mode of winding the wires of the secondary, by 

 which he obtained six inches sparks. This letter was published in 

 the September number of London Ed. Phil. Mag., 1857, vol. 

 14, page 239. 



In a subsequent letter to the editors of this magazine, Boston, 

 October 2d, 1857, Mr. Ritchie states that he constructed a coil for 

 Columbia College, New York, in July, 1857, which gave sparks 

 "ten and a half inches long." 



In The Edinburgh Nefio Philosophical Journal, vol. 6, page 189, 

 July, 1857, is a communication from Prof. William B. Rogers. 



